.DLS - DownLoadable Sounds level 1 & 2 / Mobile DLS

Saving to the 'DLS level 1' file format will gives you files compatible with the DLS synthesizer architecture level 1, which is designed to be compatible across a wide range of synthesizers.

Similarly, saving to the 'DLS level 2' file format will gives you files compatible with the DLS synthesizer architecture level 2, which is designed to be compatible with the latest (and greatest) of the more 'capable' PC wavetable synthesizer soundcards.
The files conforms to the DLS v2.2 update of the specification (backwards compatible to the original v2.0).

The 'DLS level 2+' file format option is just like 'DLS level 2' but with the addition of support for several compressed waveform data formats. These are supported by DirectMusic / DirectX v9.
Note, that the program does not use 'wave-format-extensible' for compressed waveforms when writing files - something which is suggested by DLS v2.2. But no other known implementation (that supports compressed waveforms) does either...

The 'DLS level 2++' file format option is an extension that is proprietary to Awave Studio. It just like 'DLS level 2+' but also support for several additional parameters so that it is able to store all parameters supported by Awave Studio.